在Python3中，你可以在函数参数列表中使用一个星号“*”来强制调用者只能使用关键字参数

# In Python 3 you can use a bare "*" asterisk
# in function parameter lists to force the
# caller to use keyword arguments for certain
# parameters:

>>> def f(a, b, *, c='x', d='y', e='z'):
...     return 'Hello'

# To pass the value for c, d, and e you 
# will need to explicitly pass it as 
# "key=value" named arguments:
>>> f(1, 2, 'p', 'q', 'v')
TypeError: 
"f() takes 2 positional arguments but 5 were given"

>>> f(1, 2, c='p', d='q',e='v')
'Hello'